Imaging lens system, camera module, in-vehicle system, mobile object

Abstract

To provide an imaging lens system which has sufficient brightness and a sufficient angle of view for monitoring the inside of a cabin during nighttime and a small sensor incident angle, and is less affected by changes in ambient temperature, and to provide a camera module, in-vehicle system, and mobile object.SOLUTION: An imaging lens system 11 is comprised of a front group Gf, an aperture stop STOP, and a rear group Gr comprised of substantially five lenses which are comprised of a first lens L1 with negative power having a concave surface on the image side, an aperture stop STOP, a second lens L2 with positive power having a convex surface on the image side, a third lens L3 with power, a fourth lens L4 with power, and a fifth lens L5 with power, and the imaging lens system 11 satisfies the following conditional expressions (1), (2): -1.5<f1 / f<-0.8 ...(1), f345 / f>2 ...(2), where f1 represents a focal length of the first lens L1, f represents a focal length of the entire optical system, and f345 represents a composite focal length of the third, fourth, and fifth lenses L3, L4, L5.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an imaging lens system, a camera module, an in-vehicle system, and a moving body.

Background Art

[0002] Patent Document 1 describes an imaging lens system mounted on a wide variety of imaging devices such as a camera device for photography, an in-vehicle camera device, a stereo camera device, an inspection camera device, and a surveillance camera device. The imaging lens system consists of five lenses, has an F-number of 1.9, and an overall angle of view of 118°.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the imaging lens system described in Patent Document 1, since the F-number is 1.9, the brightness is insufficient for monitoring inside the vehicle at night and for sensing at night or in bad weather. Further, in the imaging lens system described in Patent Document 1, since the overall angle of view is 118°, the angle of view is narrow for monitoring the driver, the front passenger, and the rear seat passengers inside the vehicle. Also, the incident angle of the chief ray on the image sensor (hereinafter referred to as the "sensor incident angle") increases in a bright optical system with a small F-number. When the sensor incident angle is large, incident light enters the wiring layer or the like at the peripheral portion of the image sensor and does not reach the light receiving surface (imaging surface) of the image sensor, resulting in a decrease in the amount of light received by the image sensor. However, Patent Document 1 does not mention the sensor incident angle.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide an imaging lens system, a camera module, an in-vehicle system, and a moving body that have sufficient brightness and an imaging angle for monitoring inside a vehicle at night, have a small sensor incident angle, and are less affected by temperature changes in the environment.

Means for Solving the Problems

[0006] The imaging lens system according to one embodiment is composed of a front group, an aperture stop, and substantially five lenses of a rear group in order from the object side to the image side, and includes a first lens having a negative power with an image-side surface facing concave toward the image side, the aperture stop, a second lens having a positive power with an image-side surface facing convex toward the image side, a third lens having a power, a fourth lens having a power, and a fifth lens having a power. When the focal length of the first lens is defined as f1, the focal length of the entire optical system is defined as f, and the combined focal length of the third lens, the fourth lens, and the fifth lens is defined as f345, the following conditional expressions (1) and (2) are satisfied. -1.5 < f1 / f < -0.8 ···(1) f345 / f > 2 ···(2)

Advantages of the Invention

[0007] According to the present invention, it is possible to provide an imaging lens system, a camera module, an in-vehicle system, and a moving body that have sufficient brightness and an imaging angle for monitoring inside a vehicle at night, have a small sensor incident angle, and are less affected by temperature changes in the environment.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment can realize a highly reliable system particularly in a sensing system and contributes to the development of a resilient infrastructure. It targets "9. Build the foundation of industry and technological innovation" of the Sustainable Development Goals (SDGs) proposed by the United Nations, specifically, "9.1 Develop high-quality, reliable, sustainable, and resilient infrastructure, including regional and cross-border infrastructure, to support economic development and human well-being with a focus on affordable and equitable access for all people." (Embodiment 1: Imaging Lens System) The imaging lens system according to Embodiment 1 is composed of, in order from the object side to the image side, a front group, an aperture stop, and substantially five lenses in the rear group, and includes a first lens having a negative power with its image-side surface facing concave toward the image side, the aperture stop, a second lens having a positive power with its image-side surface facing convex toward the image side, a third lens having power, a fourth lens having power, and a fifth lens having power. When the focal length of the first lens is defined as f1, the focal length of the entire optical system is defined as f, and the combined focal length of the third, fourth, and fifth lenses is defined as f345, the following conditional expressions (1) and (2) are satisfied. -1.5 < f1 / f < -0.8 ···(1) f345 / f > 2 ···(2)

[0010] Thereby, it is possible to provide an imaging lens system that has sufficient brightness and a viewing angle for monitoring inside a vehicle at night, has a small sensor incident angle, and has reduced influence due to temperature changes in the environment. Specifically, when the angle of view of the imaging lens system is widened, the diameter of the light incident on the imaging lens system becomes thicker, the effective radius of the lens for light rays becomes larger, and particularly, aberration correction is required in the peripheral portion within the effective radius of the lens for light rays. Here, the "effective radius of light rays" is the distance from the optical axis to the maximum peripheral light ray passing through the lens surface. Similarly, when the F value (F number, Fno) is decreased, the effective radius of the lens for light rays becomes larger, and particularly, aberration correction is required in the peripheral portion within the effective radius of the lens for light rays. By satisfying the above conditional expression (1), various aberrations such as field curvature and distortion aberration can be corrected, and an imaging lens system with high resolution, sufficient brightness, and a sufficient angle of view can be realized. More specifically, when the value of f1 / f is -0.8 or more, the power of the first lens is too strong, and various aberrations such as field curvature and distortion aberration in the peripheral portion within the effective radius of the first lens are excessively corrected. On the other hand, when the value of f1 / f is -1.5 or less, the power of the first lens is too weak, and various aberrations such as field curvature and distortion aberration in the peripheral portion within the effective radius of the first lens cannot be sufficiently corrected. The upper limit value of f1 / f is more preferably -0.9, -1.0, and even more preferably -1.1. The lower limit value of f1 / f is more preferably -1.4, and even more preferably -1.3. Also, by satisfying the above conditional expression (2), the amount of focus shift due to a change in the ambient temperature of the third lens, the fourth lens, and the fifth lens can be suppressed, and the influence due to a change in the ambient temperature can be reduced. More specifically, when the value of f345 / f is 2 or less, the power of the third lens, the fourth lens, and the fifth lens is too strong, and the amount of focus shift due to a change in the ambient temperature of the third lens, the fourth lens, and the fifth lens cannot be sufficiently suppressed, making it difficult to realize an imaging lens system with high resolution, sufficient brightness, and a sufficient angle of view. The lower limit value of f345 / f is more preferably 3.0, 3.1, 3.2, and even more preferably 3.5. Also, by disposing the aperture stop between the first lens and the second lens, the sensor incident angle can be reduced, and a decrease in the amount of light in the peripheral portion of the image sensor can be prevented. Here, with reference to FIG. 1, the sensor incident angle and the light condensing angle will be described. As shown in FIG. 1, the sensor incident angle is the angle CRA formed by the principal ray CR of the light incident on the image sensor and the perpendicular to the light receiving surface (imaging surface) RS of the image sensor, and increases as it goes from the center (the intersection point P with the optical axis) of the image sensor toward the peripheral portion. Also, the light condensing angle is the angle Θ formed by the lower ray LR (or the upper ray UR) of the light condensed at the intersection point P between the image sensor and the optical axis and the principal ray CR. When the numerical aperture is defined as NA, the refractive index of the medium through which the light propagates is defined as n, and the light condensing angle is defined as Θ, NA = n × sin Θ holds, and since the F-number = 1 / (2 × NA), the F-number = 1 / (2n × sin Θ). Therefore, when the F-number becomes smaller, the light condensing angle Θ becomes larger. When the light condensing angle Θ is large and furthermore the sensor incident angle CRA is large, in the peripheral portion, the light incident on the image sensor enters the wiring layer or the like of the image sensor and does not reach the light receiving surface RS of the image sensor, and the amount of light received by the image sensor decreases. In other words, as it goes toward the peripheral portion of the image sensor, the sensor incident angle CRA becomes larger, and the amount of light received by the image sensor decreases. However, in the imaging lens system according to Embodiment 1, by disposing the aperture stop between the first lens and the second lens, the sensor incident angle can be reduced, and a decrease in the amount of light in the peripheral portion of the image sensor can be prevented. Therefore, an imaging lens system that satisfies the conditional expressions (1) and (2) and has a sufficient brightness and a viewing angle for monitoring the inside of a vehicle at night, a small sensor incident angle, and a reduced influence due to temperature changes in the environment can be provided by disposing the aperture stop between the first lens and the second lens.

[0011] Also, when the focal length of the second lens is defined as f2, the imaging lens system preferably satisfies the following conditional expression (3). 1.0 < f2 / f < 1.7 ···(3) When the imaging lens system satisfies the above conditional expression (3), spherical aberration, coma, etc. can be preferably corrected in the second lens, and an imaging lens system having high resolution, sufficient brightness, and an angle of view can be realized. Specifically, when the value of f2 / f is 1.0 or less, the focal length of the second lens is too short with respect to the focal length of the entire optical system. In other words, the positive power of the second lens is too strong, and spherical aberration, coma, etc. are excessively corrected. On the other hand, when the value of f2 / f is 1.7 or more, the focal length of the second lens is too long with respect to the focal length of the entire optical system. In other words, the positive power of the second lens is too weak, and spherical aberration, coma, etc. cannot be sufficiently corrected. The lower limit value of f2 / f is more preferably 1.3, and even more preferably 1.4. The upper limit value of f2 / f is more preferably 1.6, and even more preferably 1.5.

[0012] Also, when the imaging lens system defines the combined focal length of the first lens and the second lens as f12, it is preferable to satisfy the following conditional expression (4). f12 / f < 2 ···(4) When the imaging lens system satisfies the above conditional expression (4), the amount of focus shift due to a change in the temperature of the environment of the first lens and the second lens can be suppressed, and the influence due to a change in the temperature of the environment can be reduced. More specifically, when the value of f12 / f is 2 or more, the powers of the first lens and the second lens are too strong, and the amount of focus shift due to a change in the temperature of the environment of the first lens and the second lens cannot be sufficiently suppressed, making it difficult to realize an imaging lens system having high resolution, sufficient brightness, and an angle of view. The upper limit value of f12 / f is more preferably 1.7, 1.6, 1.5, and even more preferably 1.4.

[0013] Also, when the imaging lens system defines the focal length of the third lens as f3, it is preferable to satisfy the following conditional expression (5). -10 < f3 / f < -3 ···(5) By satisfying the above conditional expression (5), the imaging lens system can preferably correct lateral aberration and field curvature, and realize an imaging lens system with high resolution, sufficient brightness, and a sufficient angle of view. Specifically, when the value of f3 / f is -3 or more, the focal length of the third lens is too short with respect to the focal length of the entire optical system. In other words, the power of the third lens is too strong, and lateral aberration and field curvature are overly corrected. On the other hand, when the value of f3 / f is -10 or less, the focal length of the third lens is too long with respect to the focal length of the entire optical system. In other words, the power of the third lens is too weak, and lateral aberration and field curvature cannot be sufficiently corrected. The lower limit value of f3 / f is more preferably -9, and even more preferably -8. Also, the upper limit value of f3 / f is more preferably -4, and even more preferably -5.

[0014] Further, when the focal length of the fourth lens is defined as f4, the imaging lens system preferably satisfies the following conditional expression (6). 2 < f4 / f < 10 ···(6) By satisfying the above conditional expression (6), the imaging lens system can preferably correct lateral aberration and field curvature, and realize an imaging lens system with high resolution, sufficient brightness, and a sufficient angle of view. Specifically, when the value of f4 / f is 2 or less, the focal length of the fourth lens is too short with respect to the focal length of the entire optical system. In other words, the power of the fourth lens is too strong, and lateral aberration and field curvature are overly corrected. On the other hand, when the value of f4 / f is 10 or more, the focal length of the fourth lens is too long with respect to the focal length of the entire optical system. In other words, the power of the fourth lens is too weak, and lateral aberration and field curvature cannot be sufficiently corrected. The lower limit value of f4 / f is more preferably 3, and even more preferably 4. Also, the upper limit value of f4 / f is more preferably 7, and even more preferably 6.

[0015] Further, when the focal length of the fifth lens is defined as f5, the imaging lens system preferably satisfies the following conditional expression (7). 3 < f5 / f < 15 ···(7) By satisfying the above conditional expression (7) for the imaging lens system, it is possible to suitably correct lateral aberration and field curvature, and to realize an imaging lens system having high resolution, sufficient brightness, and an angle of view. Specifically, when the value of f5 / f is 3 or less, the focal length of the fifth lens is too short with respect to the focal length of the entire optical system. In other words, the power of the fifth lens is too strong, and lateral aberration and field curvature are excessively corrected. On the other hand, when the value of f5 / f is 15 or more, the focal length of the fifth lens is too long with respect to the focal length of the entire optical system. In other words, the power of the fifth lens is too weak, and lateral aberration and field curvature cannot be sufficiently corrected. The lower limit value of f5 / f is more preferably 3.5, and even more preferably 4. The upper limit value of f5 / f is more preferably 11, and even more preferably 10.

[0016] Further, it is preferable that the first lens and the second lens are glass lenses, and the third lens, the fourth lens, and the fifth lens are plastic lenses. By using a glass lens for the first lens, it is possible to provide an imaging lens system that is less likely to be damaged, is resistant to oil stains, and has excellent environmental resistance. In addition, by using glass lenses with a relatively small linear expansion coefficient for the first lens and the second lens, the powers of the first lens and the second lens can be made stronger than those of other lenses, and it becomes possible to compensate for the amount of focus shift due to temperature changes in the environment by the first lens and the second lens. On the other hand, by using plastic lenses for the third lens, the fourth lens, and the fifth lens, the manufacturing cost can be reduced.

[0017] In the imaging lens system, it is preferable that the first lens has the largest negative power. Thereby, it becomes possible to compensate for the amount of focus shift due to temperature changes in the environment of other lenses having positive power by the first lens.

[0018] In the imaging lens system, it is preferable that the second lens has the largest positive power. Thereby, it becomes possible to compensate for the amount of focus shift due to temperature changes in the environment of other lenses having negative power by the second lens.

[0019] Also, the second lens is preferably an aspherical lens. By the second lens being an aspherical lens, various aberrations such as spherical aberration and lateral aberration can be corrected, and an imaging lens system with high resolution, sufficient brightness, and an adequate angle of view can be realized.

[0020] Also, when defining the distance on the optical axis between the image side surface of the fifth lens and the light receiving surface of the image sensor as BFL, it is preferable that the imaging lens system satisfies the following conditional expression (8). BFL / f > 0.9 ···(8) By the imaging lens system satisfying the above conditional expression (8), the distance between the imaging lens system and the image sensor can be ensured, and the assembly of the imaging lens system and the image sensor becomes easier. The lower limit value of BFL / f is more preferably 1.0, 1.1, still more preferably 1.2, 1.25.

[0021] Also, when defining the design wavelength of the imaging lens system as WL, it is preferable that the imaging lens system satisfies the following conditional expression (9). 800nm < WL < 1000nm ···(9) By the imaging lens system satisfying the above conditional expression (9), infrared light can be detected, enabling sensing at night or in bad weather.

[0022] Also, when defining the half angle of view of the imaging lens system as ω, it is preferable that the imaging lens system satisfies the following conditional expression (10). ω > 60° ···(10) By the imaging lens system satisfying the above conditional expression (10), an imaging lens system with a wide angle of view, high resolution, sufficient brightness, and an adequate angle of view can be realized. The lower limit value of ω is more preferably 70°.

[0023] Also, when defining the sensor incident angle of the imaging lens system as CRA, it is preferable that the imaging lens system satisfies the following conditional expression (11). CRA < 5° ···(11) By satisfying the above conditional expression (11) for the imaging lens system, the sensor incident angle can be reduced over the entire image sensor, and in particular, a decrease in the amount of light in the peripheral portion of the image sensor can be prevented.

[0024] (Embodiment 2: Camera Module) The camera module according to Embodiment 2 includes the above-described imaging lens system and an image sensor that is disposed at the focal position of the imaging lens system and converts the light condensed through the imaging lens system into an electrical signal. Thereby, it is possible to provide a camera module that has sufficient brightness and an angle of view for monitoring inside a vehicle at night, has a small sensor incident angle, and is less affected by temperature changes in the environment.

[0025] Next, examples corresponding to the imaging lens system according to Embodiment 1 and the camera module according to Embodiment 2 will be described with reference to the drawings. (Example 1) FIG. 2 is a cross-sectional view showing the configuration of the camera module 10 of Example 1. Specifically, the camera module 10 includes an imaging lens system 11 and an image sensor 12. The imaging lens system 11 and the image sensor 12 are housed in a housing (not shown).

[0026] The image sensor 12 is an element that converts the received light into an electrical signal. For example, a CCD image sensor or a CMOS image sensor is used. The image sensor 12 is disposed at the imaging position (focal position) of the imaging lens system 11.

[0027] The imaging lens system 11 according to Example 1 includes, in order from the object side toward the image side, a front group Gf including a first lens L1, an aperture stop (STOP), and a rear group Gr including a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5. The imaging plane of the imaging lens system 11 is indicated by IMG. The first lens L1 and the second lens L2 are glass lenses. The third lens L3, the fourth lens L4, and the fifth lens L5 are plastic lenses. Between the imaging lens system 11 and the imaging device 12, an optical filter (such as an infrared transmission filter, a visible / infrared band-pass filter, etc.) is arranged as necessary. In this specification, an example in which an infrared transmission filter (FILTER) is arranged between the imaging lens system 11 and the imaging device 12 will be described.

[0028] The first lens L1 is a meniscus lens having a negative power. The object side surface S1 of the first lens L1 has a spherical shape with a convex surface facing the object side. The image side surface S2 of the first lens L1 has a spherical shape with a concave surface facing the image side.

[0029] The aperture STOP is an aperture that determines the F value (F number, Fno) of the lens system. The aperture STOP is arranged between the first lens L1 and the second lens L2.

[0030] The second lens L2 is a biconvex lens having a positive power. The object side surface S5 of the second lens L2 has an aspherical shape with a convex surface facing the object side. The image side surface S6 of the second lens L2 has an aspherical shape with a convex surface facing the image side.

[0031] The third lens L3 is a meniscus lens having a negative power. The object side surface S7 of the third lens L3 has an aspherical shape with a concave surface facing the object side. Also, the image side surface S8 of the third lens L3 has an aspherical shape with a convex surface facing the image side.

[0032] The fourth lens L4 is a biconvex lens having a positive power. The object side surface S9 of the fourth lens L4 has an aspherical shape with a convex surface facing the object side. Also, the image side surface S10 of the fourth lens L4 has an aspherical shape with a convex surface facing the image side.

[0033] The fifth lens L5 is a meniscus lens having a positive power. The object side surface S11 of the fifth lens L5 has an aspherical shape with a convex surface facing the object side. Also, the image side surface S12 of the fifth lens L5 has an aspherical shape with a concave surface facing the image side.

[0034] The infrared transmission filter (FILTER) is a filter for transmitting light in the near-infrared region and cutting off light in the visible light region. The infrared transmission filter is treated as an integral part of the imaging lens system 11 during the design of the imaging lens system 11. However, the infrared transmission filter is not an essential component of the imaging lens system 11. The infrared transmission filter is disposed on the image side of the fifth lens L5. Also, a sensor cover glass may be disposed between the infrared transmission filter and the imaging device 12 to prevent dust from adhering to the imaging device 12.

[0035] Table 1 shows the lens data of each lens surface in the imaging lens system 11 of Example 1. In Table 1, as the lens data, the radius of curvature (mm) of each surface, the interval between surfaces (mm) on the optical axis OA, the refractive index n850 for a light ray of 850 nm, the refractive index nd for the d-line, the Abbe number νd for the d-line, and the effective radius of the light ray (mm) are presented. Also, in Table 1, the surfaces marked with "*" indicate aspherical surfaces. In the imaging lens system 11 of Example 1, the F value is 1.30 and the semi-field angle (ω) is 73.6°.

[0036]

Table 1

[0037] When the aspherical shape adopted for the lens surface has the sag amount Z, the reciprocal of the radius of curvature c, the conic coefficient k, and the ray height r from the optical axis OA, the aspherical coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th orders are α4, α6, α8, α 10 , α 12 , α 14 , α 16 respectively, and are represented by the following formula.

Equation

[0038] Table 2 shows the aspherical coefficients for defining the aspherical shape of the lens surfaces that are aspherical in the imaging lens system 11 of Example 1. In Table 2, for example, "-1.326785E-03" means "-1.326785 × 10 -3 ". The numerical expressions are the same for the following tables.

[0039] [Table 2]

[0040] Next, aberrations will be described with reference to the drawings. FIG. 3 shows the spherical aberration diagram (longitudinal aberration diagram), the field curvature diagram, and the distortion aberration diagram in the imaging lens system 11 of Example 1. Also, in the longitudinal aberration diagram of FIG. 3(A), the horizontal axis indicates the position where the light ray intersects the optical axis OA, and the vertical axis indicates the passing height of the light ray on the entrance pupil. Also, FIG. 3(A) shows the simulation results for the light ray of 850 nm. Also, in the field curvature diagram of FIG. 3(B), the horizontal axis indicates the distance in the direction of the optical axis OA, and the vertical axis indicates the image height (angle of view). Also, in the field curvature diagram of FIG. 3(B), Sag indicates the imaging position in the sagittal ray bundle, and Tan indicates the imaging position in the tangential ray bundle. Also, FIG. 3(B) shows the simulation results for the light ray of 850 nm. Also, in the distortion aberration diagram of FIG. 3(C), the horizontal axis indicates the distortion aberration (%) of the image, and the vertical axis indicates the image height (angle of view). Also, FIG. 3(C) shows the simulation results for the light ray of 850 nm.

[0041] (Example 2) FIG. 4 is a cross-sectional view showing the camera module 10 according to Example 2. In the imaging lens system 11 according to Example 2, the fourth lens L4 is a meniscus lens having a positive power, the object side surface S9 has an aspherical shape with a concave surface facing the object side, and the image side surface S10 has an aspherical shape with a convex surface facing the image side. Since the configuration of the imaging lens system 11 according to Example 2 other than the fourth lens L4 is the same as the lens configuration of Example 1, the description thereof is omitted. Hereinafter, the characteristic data of the imaging lens system 11 according to Example 2 will be described.

[0042] Table 3 shows the lens data of each lens surface of the imaging lens system 11 according to Example 2. Since the items shown in Table 3 are the same as those in Table 1, the description thereof is omitted. Also, in the imaging lens system 11 of Example 2, the F-number is 1.30 and the semi-field angle (ω) is 73.4°.

[0043]

Table 3

[0044] Table 4 shows the aspherical coefficients for defining the aspherical shape of the lens surfaces that are aspherical in the imaging lens system 11 of Example 2. In Table 4, the aspherical shape adopted for the lens surface is represented by the same formula as in Example 1.

[0045]

Table 4

[0046] FIG. 5 shows the spherical aberration diagram (longitudinal aberration diagram), field curvature diagram, and distortion aberration diagram in the imaging lens system 11 of Example 2. Since the description of each aberration diagram shown in FIG. 5 is the same as that in FIG. 3, the description thereof is omitted.

[0047] (Example 3) FIG. 6 is a cross-sectional view showing the camera module 10 according to Example 3. The imaging lens system 11 according to Example 3 has a biconvex lens in which the fifth lens L5 has a positive power. The object-side surface S11 has an aspherical shape with a convex surface facing the object side, and the image-side surface S12 has an aspherical shape with a convex surface facing the image side. Since the configuration other than the fifth lens L5 of the imaging lens system 11 according to Example 3 has the same lens configuration as that of Example 2, the description thereof is omitted. Hereinafter, the characteristic data of the imaging lens system 11 according to Example 3 will be described.

[0048] Table 5 shows the lens data of each lens surface of the imaging lens system 11 according to Example 3. Since the items shown in Table 5 are the same as those in Table 1, the description thereof is omitted. In addition, in the imaging lens system 11 of Example 3, the F-number is 1.31 and the semi-field angle (ω) is 73.4°.

[0049]

Table 5

[0050] Table 6 shows the aspherical coefficients for defining the aspherical shape of the lens surface that is aspherical in the imaging lens system 11 of Example 3. In Table 6, the aspherical shape adopted for the lens surface is represented by the same formula as in Example 1.

[0051]

Table 6

[0052] FIG. 7 shows the spherical aberration diagram (longitudinal aberration diagram), field curvature diagram, and distortion aberration diagram in the imaging lens system 11 of Example 3. Since the description of each aberration diagram shown in FIG. 7 is the same as that in FIG. 3, the description thereof is omitted.

[0053] (Example 4) FIG. 8 is a cross-sectional view showing the camera module 10 according to Example 4. In the imaging lens system 11 according to Example 4, the fifth lens L5 is a meniscus lens having positive power, the object side surface S11 has an aspherical shape with a concave surface facing the object side, and the image side surface S12 has an aspherical shape with a convex surface facing the image side. Since the configuration other than the fifth lens L5 of the imaging lens system 11 according to Example 4 has the same lens configuration as that of Example 2, the characteristic data of the imaging lens system 11 according to Example 4 will be described below.

[0054] Table 7 shows the lens data of each lens surface of the imaging lens system 11 according to Example 4. Since the items shown in Table 7 are the same as those in Table 1, the description thereof will be omitted. Also, in the imaging lens system 11 of Example 4, the F-number is 1.31 and the semi-field angle (ω) is 73.4°.

[0055]

Table 7

[0056] Table 8 shows the aspherical coefficients for defining the aspherical shape of the aspherical lens surfaces in the imaging lens system 11 of Example 4. In Table 8, the aspherical shape adopted for the lens surface is represented by the same formula as in Example 1.

[0057]

Table 8

[0058] FIG. 9 shows the spherical aberration diagram (longitudinal aberration diagram), field curvature diagram, and distortion aberration diagram in the imaging lens system 11 of Example 4. Since the description of each aberration diagram shown in FIG. 9 is the same as that in FIG. 3, the description thereof will be omitted.

[0059] (Example 5) FIG. 10 is a cross-sectional view showing the camera module 10 according to Example 5. In the imaging lens system 11 according to Example 5, the third lens L3 is a biconcave lens having a negative power, the object side surface S7 has an aspherical shape with a concave surface facing the object side, and the image side surface S6 has an aspherical shape with a concave surface facing the image side. Further, in the imaging lens system 11 according to Example 5, the fourth lens L4 is a biconvex lens having a positive power, the object side surface S9 has an aspherical shape with a convex surface facing the object side, and the image side surface S10 of the fourth lens L4 has an aspherical shape with a convex surface facing the image side. Since the other configuration of the imaging lens system 11 according to Example 5 has the same lens configuration as that of Example 4, the description thereof is omitted. Hereinafter, the characteristic data of the imaging lens system 11 according to Example 5 will be described.

[0060] Table 9 shows the lens data of each lens surface of the imaging lens system 11 according to Example 5. In Table 9, instead of the refractive index n850 for the light ray of 850 nm, the refractive index n940 for the light ray of 940 nm is presented. Since the other items shown in Table 9 are the same as those in Table 1, the description thereof is omitted. Further, in the imaging lens system 11 of Example 5, the F value is 1.30 and the semi-field angle (ω) is 73.6°.

[0061]

Table 9

[0062] Table 10 shows the aspherical coefficients for defining the aspherical shape of the lens surfaces that are aspherical in the imaging lens system 11 of Example 5. In Table 10, the aspherical shape adopted for the lens surface is represented by the same formula as in Example 1.

[0063]

Table 10

[0064] FIG. 11 shows the spherical aberration diagram (longitudinal aberration diagram), the field curvature diagram, and the distortion aberration diagram in the imaging lens system 11 of Example 5. Since the description of each aberration diagram shown in FIG. 11 is the same as that in FIG. 3, the description thereof is omitted.

[0065] Table 11 shows the F-number of the imaging lens system 11, the full angle of view (2ω), the focal length f of the entire optical system of the imaging lens system 11, the focal length f1 of the first lens L1, the focal length f2 of the second lens L2, the focal length f3 of the third lens L3, the focal length f4 of the fourth lens L4, the focal length f5 of the fifth lens L5, the value of f1 / f, the value of f345 / f, the value of f2 / f, the value of f12 / f, the value of f3 / f, the value of f4 / f, the value of f5 / f, the value of BFL / f, the value of WL, the value of the half angle of view (ω), and the value of the sensor incident angle CRA. In Table 11, the unit of the focal length is mm. Also, the focal lengths shown in Table 11 were calculated using the d-line.

[0066]

Table 11

[0067] In Examples 1 to 5, by the imaging lens system 11 satisfying the conditional expressions (1) and (2), it is possible to provide an imaging lens system 11 having sufficient brightness and angle of view for monitoring inside a vehicle at night, having a small sensor incident angle, and having reduced influence due to environmental temperature changes. Specifically, in Examples 1 to 5, the F-number is 1.30 to 1.31, and the imaging lens system 11 has sufficient brightness. Also, in Examples 1 to 5, as shown in FIGS. 3, 5, 7, 9, and 11, various aberrations can be preferably reduced. Therefore, in Examples 1 to 5, the imaging lens system 11 has high resolution. Also, in Examples 1 to 5, the half angle of view (ω) is 73.4° to 73.6°, and the imaging lens system 11 has a sufficiently wide angle of view for vehicle, particularly in-vehicle sensing. Also, in Examples 1 to 5, the sensor incident angle CRA is 1.90° to 4.90°, and the sensor incident angle can be sufficiently suppressed to be small.

[0068] Also, in Examples 1 to 5, by the value of f2 / f satisfying the above conditional expression (3), in the second lens L2, various aberrations such as spherical aberration and lateral aberration can be preferably corrected. Actually, in Examples 1 to 5, as shown in FIGS. 3, 5, 7, 9, and 11, various aberrations can be preferably reduced.

[0069] Also, in Examples 1 to 5, since the value of f12 / f satisfies the above conditional expression (4), the amount of focus shift due to the temperature change of the environment can be sufficiently suppressed. Table 12 shows the amount of focus shift (μm) of the imaging lens system 11 of Examples 1 to 5 accompanying the temperature change of the environment. Table 12 shows the amount of focus shift on the optical axis from the focal length f at room temperature of 25°C. Further, the materials of the barrel and the housing used for calculating the amount of focus shift of the focal length f shown in Table 12 are XYRON XP640 manufactured by Asahi Kasei Corporation. As shown in Table 12, in Examples 1 to 5, the amount of focus shift due to the temperature change of the environment can be sufficiently suppressed. The amount of focus shift of the focal length f shown in Table 12 was calculated using the design wavelength. The design wavelength is 850 nm in Examples 1 to 4, and the design wavelength is 940 nm in Example 5.

Table 12

[0070] Also, in Examples 1 to 5, since the value of f3 / f satisfies the above conditional expression (5), various aberrations such as lateral aberration and field curvature can be preferably corrected in the third lens L3. Actually, in Examples 1 to 5, as shown in FIGS. 3, 5, 7, 9, and 11, various aberrations can be preferably reduced.

[0071] Also, in Examples 1 to 5, since the value of f4 / f satisfies the above conditional expression (6), various aberrations such as lateral aberration and field curvature can be preferably corrected in the fourth lens L4. Actually, in Examples 1 to 5, as shown in FIGS. 3, 5, 7, 9, and 11, various aberrations can be preferably reduced.

[0072] Also, in Examples 1 to 5, since the value of f5 / f satisfies the above conditional expression (7), various aberrations such as lateral aberration and field curvature can be preferably corrected in the fifth lens L5. Actually, in Examples 1 to 5, as shown in FIGS. 3, 5, 7, 9, and 11, various aberrations can be preferably reduced.

[0073] Further, in Embodiments 1 to 5, since the second lens L2 is an aspherical lens, various aberrations such as spherical aberration and coma aberration can be suitably corrected in the second lens L2. In fact, in Embodiments 1 to 5, as shown in FIGS. 3, 5, 7, 9, and 11, various aberrations can be suitably reduced.

[0074] Further, in Embodiments 1 to 5, since the value of BFL / f satisfies the above conditional expression (8), the distance between the imaging lens system and the image sensor can be ensured, and the assembly of the imaging lens system and the image sensor becomes easier.

[0075] Further, in Embodiments 1 to 5, since the value of WL satisfies the above conditional expression (9), infrared light can be detected, enabling sensing at night or in bad weather.

[0076] Further, in Embodiments 1 to 5, the value of the half field angle ω satisfies the above conditional expression (10), and the imaging lens system 11 has a sufficiently wide field angle for sensing in a vehicle, particularly inside the vehicle.

[0077] Further, in Embodiments 1 to 5, since the value of the sensor incident angle CRA satisfies the above conditional expression (11), the sensor incident angle can be reduced over the entire image sensor, and in particular, a decrease in the amount of light in the peripheral portion of the image sensor can be prevented.

[0078] Further, since the camera module 10 includes the imaging lens system 11, a camera module 10 can be provided that has sufficient brightness and a field angle for monitoring the inside of the vehicle at night, has a small sensor incident angle, and is less affected by environmental temperature changes.

[0079] (Embodiment 3) FIG. 12 is a schematic diagram of a vehicle 40 equipped with an in-vehicle system including an imaging lens system 11 according to Embodiment 1 or Embodiment 2 and an imaging device 12 that converts light collected through the imaging lens system 11 into an electrical signal. As shown in the figure, the imaging device 50 can be mounted on the vehicle 40, and FIG. 12 is an arrangement example illustrating the mounting position of the imaging device 50 in the vehicle 40. The imaging device 50 mounted on the vehicle 40 can also be called an in-vehicle camera and can be installed in various locations of the vehicle 40. For example, the first imaging device 50a may be arranged on the front bumper or in the vicinity thereof as a camera for monitoring the front when the vehicle 40 is running. Also, the second imaging device 50b for monitoring the front may be arranged in the vicinity of the inner rearview mirror in the passenger compartment of the vehicle 40. The third imaging device 50c may be arranged on the dashboard or inside the instrument panel as a camera for monitoring the driving situation of the driver. The fourth imaging device 50d may be installed at the rear of the vehicle 40 for rear monitoring of the vehicle 40. The imaging devices 50a and 50b can be called front cameras. The third imaging device 50c can be called an in-camera. The fourth imaging device 50d can be called a rear camera. The imaging device 50 is not limited to these and includes imaging devices installed at various positions such as a left side camera for imaging the left rear side and a right side camera for imaging the right rear side.

[0080] The image signal of the image captured by the imaging device 50 can be output to the information processing device 42 and / or the display device 43 in the vehicle 40. These information processing device 42 and display device 43, together with the imaging device 50, constitute an in-vehicle system. The information processing device 42 in the vehicle 40 includes a device that processes the image signal acquired by the imaging device 50, recognizes various objects in the captured image, and supports the driver's driving. Further, the information processing device 42 includes, for example, a navigation device, a collision damage mitigation brake device, an inter-vehicle distance control device, and a lane departure warning device, etc., but is not limited thereto. The display device 43 displays the image processed and output by the information processing device 42, but can also directly receive the image signal from the imaging device 50. Further, the display device 43 can employ a liquid crystal display (LCD), an organic EL (Electro-Luminescence) display, and an inorganic EL display, but is not limited thereto. The display device 43 can display the image signal output from the imaging device 50 that captures an image at a position difficult to visually recognize by the driver, such as a rear camera, to passengers such as the driver.

[0081] FIG. 13 shows the configuration of the imaging device 50 that constitutes the in-vehicle system of FIG. 12. As shown in the figure, the imaging device 50 according to an embodiment includes a control unit 52, a storage unit 54, and a camera module 10.

[0082] The control unit 52 controls the camera module 10 and processes the electrical signal output from the imaging element 12 of the camera module 10. This control unit 52 may be configured as a processor, for example. Further, the control unit 52 may include one or more processors. The processor may include a general-purpose processor that reads a specific program and executes a specific function, and a dedicated processor specialized for a specific process. The dedicated processor may include an application-specific integrated circuit (IC). The application-specific IC is also referred to as an application-specific integrated circuit (ASIC). The processor may include a programmable logic device. The programmable logic device is also referred to as a programmable logic device (PLD). The PLD may include a field-programmable gate array (FPGA). The control unit 52 may be either a system-on-a-chip (SoC) or a system-in-a-package (SiP) in which one or more processors cooperate.

[0083] The storage unit 54 stores various information or parameters related to the operation of the imaging device 50. The storage unit 54 may be configured as, for example, a semiconductor memory or the like. The storage unit 54 may function as a work memory of the control unit 52. The storage unit 54 may store the captured image. The storage unit 54 may store various parameters and the like for the control unit 52 to perform detection processing based on the captured image. The storage unit 54 may be included in the control unit 52.

[0084] As described above, the camera module 10 captures an object image formed through the imaging lens system 11 with the imaging element 12 and outputs the captured image. The image captured by the camera module 10 is also referred to as a captured image.

[0085] The imaging device 12 may be composed of, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, a CCD (Charge Coupled Device), or the like. The imaging device 12 has an imaging surface on which a plurality of pixels are arranged. Each pixel outputs a signal specified by a current or a voltage according to the amount of incident light. The signal output from each pixel is also referred to as imaging data.

[0086] The imaging data may be read out by the camera module 10 for all the pixels and taken into the control unit 52 as an imaging image. The imaging image read out for all the pixels is also referred to as the maximum imaging image. The imaging data may be read out by the camera module 10 for some of the pixels and taken in as an imaging image. In other words, the imaging data may be read out from the pixels within a predetermined capture range. The imaging data read out from the pixels within the predetermined capture range may be taken in as an imaging image. The predetermined capture range may be set by the control unit 52. The camera module 10 may acquire the predetermined capture range from the control unit 52. The imaging device 12 may image an image within a predetermined capture range of the subject image formed through the imaging lens system 11.

[0087] Note that the present invention is not limited to the above embodiments, and can be appropriately modified without departing from the spirit thereof. For example, the application of the imaging lens system of the present invention is not limited to in-vehicle cameras and surveillance cameras, and can also be used for other applications such as being mounted on small electronic devices such as mobile phones.

Explanation of Reference Numerals

[0088] 10 Camera module 11 Imaging lens system 12 Imaging device 40 Vehicle (moving body) 42 Information processing device (processing device) 43 Display device (output device) 50 Imaging apparatus 52 Control unit L1 First lens L2 Second lens L3 Third lens L4 Fourth lens L5 Fifth lens STOP Diaphragm Gf Front group Gr Rear group FILTER Infrared transmission filter IMG Imaging plane OA Optical axis

Claims

1. Comprising, in order from the object side toward the image side, a front group, an aperture stop, and substantially five lenses of a rear group, including a first lens having a negative power with its image-side surface facing concave toward the image side, the aperture stop, a second lens having a positive power with its image-side surface facing convex toward the image side, a third lens having a power, a fourth lens having a power, and a fifth lens having a power, characterized in that when the focal length of the first lens is defined as f1, the focal length of the entire optical system is defined as f, and the combined focal length of the third lens, the fourth lens, and the fifth lens is defined as f345, the following conditional expressions (1) and (2) are satisfied, an imaging lens system. -1.5 < f1 / f < -0.8... (1) f345 / f > 2... (2)

2. characterized in that when the focal length of the second lens is defined as f2, the following conditional expression (3) is satisfied, the imaging lens system according to Claim 1. 1.0 < f2 / f < 1.7... (3)

3. characterized in that when the combined focal length of the first lens and the second lens is defined as f12, the following conditional expression (4) is satisfied, the imaging lens system according to Claim 1. f12 / f < 2... (4)

4. characterized in that when the focal length of the third lens is defined as f3, the following conditional expression (5) is satisfied, the imaging lens system according to Claim 1. -10 < f3 / f < -3... (5)

5. characterized in that when the focal length of the fourth lens is defined as f4, the following conditional expression (6) is satisfied, the imaging lens system according to Claim 1. 2 < f4 / f < 10... (6)

6. characterized in that when the focal length of the fifth lens is defined as f5, the following conditional expression (7) is satisfied, the imaging lens system according to Claim 1. 3 < f5 / f < 15... (7)

7. wherein the first lens and the second lens are glass lenses, and the third lens, the fourth lens, and the fifth lens are plastic lenses, the imaging lens system according to Claim 1.

8. in the imaging lens system, the first lens has the largest negative power, the imaging lens system according to Claim 1.

9. in the imaging lens system, the second lens has the largest positive power, the imaging lens system according to Claim 1.

10. the second lens is an aspherical lens, the imaging lens system according to Claim 1.

11. When the distance on the optical axis between the image side surface of the fifth lens and the light receiving surface of the image sensor is defined as BFL, the imaging lens system according to claim 1, characterized in that the following conditional expression (8) is satisfied. BFL / f > 0.9... (8)

12. When the design wavelength of the imaging lens system is defined as WL, the imaging lens system according to claim 1, characterized in that the following conditional expression (9) is satisfied. 800 nm < WL < 1000 nm... (9)

13. When the half field angle of the imaging lens system is defined as ω, the imaging lens system according to claim 1, characterized in that the following conditional expression (10) is satisfied. ω > 60°... (10)

14. When the sensor incident angle of the imaging lens system is defined as CRA, the imaging lens system according to claim 1, characterized in that the following conditional expression (11) is satisfied. CRA < 5°... (11)

15. A camera module comprising the imaging lens system according to any one of claims 1 to 14, and an imaging device that converts the light condensed through the imaging lens system into an electrical signal.

16. An in-vehicle system mounted on a vehicle, The camera module according to claim 15, and An information processing device that processes the captured image output from the imaging device of the camera module and recognizes an object in the captured image. An in-vehicle system characterized by comprising.

17. A moving body equipped with the in-vehicle system according to claim 16, The in-vehicle system further includes an output device that outputs information to the occupant, The information processing device is configured to output the recognition information of the object to the output device. A moving body characterized by this.

Images